High durability geopolymer recycled concrete for coastal engineering and a method of manufacturing the same

Abstract

This invention discloses a high-durability geopolymer recycled concrete for coastal engineering and its preparation method, belonging to the field of concrete application and preparation technology. It consists of geopolymer cementitious materials, recycled aggregates, manufactured sand, water, water-reducing agents, and auxiliary materials. The auxiliary materials are modifiers and synergists. The geopolymer cementitious materials are composed of industrial solid waste steel slag, gypsum, mineral powder, metal tailings, and solid alkali activators. The recycled aggregates are obtained from construction solid waste through crushing, washing, and sorting. The modifier is nano-sized magnesium hydroxysilicate, and the synergist is modified chitosan microspheres. This invention utilizes "industrial solid waste + construction solid waste recycling," selecting two novel auxiliary materials—nano-sized magnesium hydroxysilicate and irradiated modified chitosan microspheres—to form a unique three-dimensional material system, effectively solving the problems of uneven concrete performance and insufficient durability in coastal environments.

Description

Technical Field

[0001] This invention belongs to the field of concrete application and preparation technology, specifically relating to a high-durability geopolymer recycled concrete for coastal engineering and its preparation method. Background Technology

[0002] In recent years, with the continuous advancement of urbanization, especially the comprehensive rollout of urban redevelopment projects, construction solid waste has increased significantly. This not only restricts the sustainable development of cities but also encroaches on large amounts of arable land and pollutes the ecological environment. It is estimated that the annual output of construction solid waste will exceed 3 billion tons in the next 5-10 years. Achieving its large-scale disposal is both a key and challenging aspect of the concrete industry's green and low-carbon transformation.

[0003] Recycled aggregate concrete, as a key technology for the resource utilization of construction solid waste, has significant advantages in reducing the consumption of natural resources and lowering carbon emissions. However, the loose and porous cement mortar remaining on the surface of recycled aggregates and the micro-cracks generated during crushing and screening lead to a decrease in the strength and elastic modulus of the concrete, an increase in shrinkage and creep, and a significant decline in durability. Coastal areas, as the most economically vibrant regions in my country, place higher demands on the performance of concrete materials in coastal engineering construction. However, under the influence of corrosive media in coastal areas (such as chloride and sulfate ions), the mechanical properties and durability of recycled aggregate concrete degrade even more significantly, severely limiting its widespread application in coastal engineering structures.

[0004] Therefore, developing green and low-carbon concrete suitable for coastal bridges and modular building structures, and improving its durability and service performance, is not only a key measure to promote the resource utilization of construction solid waste, but also an important breakthrough for achieving the green and low-carbon transformation of the concrete industry. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a high-durability geopolymer recycled concrete for coastal engineering and its preparation method, so as to solve the problem of insufficient application of concrete in coastal engineering building structures.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a high-durability geopolymer recycled concrete for coastal engineering, which is composed of geopolymer cementitious materials, recycled aggregates, manufactured sand, water, water-reducing agent, and auxiliary materials, wherein the auxiliary materials are modifiers and synergists; The geopolymer cementitious material is composed of industrial solid waste steel slag, gypsum, mineral powder, metal tailings and solid alkali activator; The recycled aggregate is produced from construction solid waste through crushing, washing, and sorting. The modifier is nano-sized magnesium hydroxysilicate; The synergistic agent is modified chitosan microspheres.

[0007] Furthermore, the geopolymer cementitious material comprises 400-550 parts, recycled aggregate comprises 1090-1140 parts, manufactured sand comprises 670-700 parts, water comprises 140-160 parts, water-reducing agent comprises 6.0-8.3 parts, modifier comprises 2.5%-4.0% of the mass of the geopolymer cementitious material, and synergistic agent comprises 1.0%-2.0% of the mass of the geopolymer cementitious material.

[0008] Furthermore, the modified chitosan microspheres are modified by γ-ray irradiation with an irradiation dose of 5-8 kGy.

[0009] Furthermore, a method for preparing high-durability geopolymer recycled concrete for coastal engineering includes the following steps: S1. Place the recycled aggregate in a concrete carbonation test chamber for 24 hours of carbonation treatment; then place the recycled aggregate in a vacuum drying oven for 2-3 hours to remove surface moisture; then place it in a plasma treatment instrument and continue to treat it for 8-12 minutes using argon as the gas source to complete the pretreatment. S2. Prepare a nano-silica dispersion and spray it onto the surface of the pretreated recycled aggregate to form a nano-silica film. Let it dry for 30-60 minutes, then spray a nano-hydroxy magnesium silicate dispersion to fill the micropores on the aggregate surface and complete the modification and reinforcement treatment of the recycled aggregate. S3. Add nano-hydroxy magnesium silicate to deionized water, then add dispersant and ultrasonically disperse. Subsequently, add silane coupling agent KH-550 and stir at 57-65℃ for 1-1.5h to complete the surface activation of the modifier. Add modified chitosan microspheres to water and stir evenly. S4. Weigh out the geopolymer cementitious material, recycled aggregate, manufactured sand, water, water-reducing agent and pretreated auxiliary materials according to the proportions. Add the geopolymer cementitious material, manufactured sand and 50% water to the mixer and mix to obtain a uniform mortar mixture. S5. Add the modified and reinforced recycled aggregate to the mortar mixture and stir at 300-400 rpm for 15-20 minutes. Then increase the speed to 500-600 rpm and add nano-hydroxy magnesium silicate and stir for 30-40 minutes. Then raise the temperature to 85-95℃, reduce the stirring speed to 200-300 rpm, add modified chitosan microspheres, water-reducing agent, and the remaining 50% of water and continue stirring to obtain the concrete mixture. S6. Pour the concrete mixture into a mold for curing at 18-22℃ and ≥90% humidity for 7-14 days. After curing, transfer it to a constant temperature curing chamber and cure at 68-75℃ for 4-6 hours. Then, allow it to cool naturally to room temperature for 12-15 hours. Finally, treat it with ultraviolet light to obtain high-durability recycled polymer concrete.

[0010] Furthermore, in step S1, the temperature of the carbonization test chamber is 20℃, the humidity is 70%, and the carbon dioxide concentration is 20%; the temperature of the vacuum drying oven is 75-85℃, the vacuum degree is -0.08~-0.07MPa, and the drying time is 2-3 hours; the power during argon treatment is 150-200W.

[0011] Further, in step S2, after spraying the nano-silica dispersion, it is air-dried for 30-60 minutes; in step S3, during ultrasonic dispersion, the power is 300-350W and the time is 20-30 minutes; the dispersant accounts for 0.1%-0.2% of the deionized water, and the silane coupling agent KH-550 accounts for 0.5%-0.8% of the deionized water.

[0012] Furthermore, in step S6, the ultraviolet light irradiation treatment is performed with a wavelength of 254nm, an irradiation intensity of 10-15mW / cm², and an irradiation time of 10-15min.

[0013] The beneficial effects of this invention are as follows: 1. This invention utilizes "industrial solid waste + construction solid waste recycling" and selects two novel auxiliary materials, nano-hydroxy magnesium silicate and irradiated modified chitosan microspheres, to form a unique three-dimensional material system, which can effectively solve the problems of uneven performance of existing concrete and insufficient durability in coastal environments.

[0014] 2. This invention achieves a simultaneous leap forward in both the high content and performance of recycled aggregates, breaking through the bottlenecks of traditional applications. In existing technologies, due to performance defects, high-content recycled aggregates inevitably lead to a decline in concrete performance, thus typically only replacing natural aggregates at a low proportion of 30%-40%. This technology, through synergistic modification, achieves for the first time 100% complete replacement of natural aggregates with recycled aggregates, and the resulting concrete exhibits significantly superior mechanical properties compared to traditional recycled concrete, reaching a strength grade of C50. This breaks down the technical barrier that "high content" and "high performance" are mutually exclusive, providing a fundamental solution for the large-scale, high-value utilization of construction solid waste.

[0015] 3. This invention achieves high system densification through dual modification. The densified microstructure greatly blocks the transmission channels of chloride ions, oxygen and moisture. The 56-day electrical flux of the concrete is less than 500 coulombs, achieving excellent resistance to chloride ion penetration. It can effectively protect the internal steel bars of the building structure, solve the most serious steel bar corrosion problem in coastal environments, and bring about a qualitative improvement in durability, enabling it to meet the stringent requirements of coastal building structures.

[0016] 4. This invention boasts significant advantages in environmental friendliness, energy efficiency, and operability. It avoids the use of hazardous chemicals that may cause secondary pollution, making the carbonization and nanomaterial processing cleaner and safer. Compared to mechanical grinding and strengthening, this method eliminates the need for energy-intensive physical crushing and grinding equipment, significantly reducing energy consumption and processing costs. Compared to technologies such as microbial induced deposition (MICP), this method is more mature and stable, with a faster reaction rate. It does not require complex microbial cultivation and long-term maintenance conditions, resulting in lower costs and easier industrial control. Furthermore, this method can consume and store carbon dioxide emitted from industrial processes as reactants, directly reducing greenhouse gases and giving the technology an active carbon negative effect, highly aligning with the national "dual carbon" policy.

[0017] Other advantages, objectives, and features of the invention will be set forth in the following description and will be apparent to those skilled in the art in some respects, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0018] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 This is a flowchart illustrating the preparation process of the present invention; Figure 2 This is a diagram illustrating the concrete material used in this invention. Detailed Implementation

[0019] like Figures 1-2 As shown, this invention discloses a method for preparing high-durability geopolymer recycled concrete for coastal engineering.

[0020] Example 1 S1. Place the recycled aggregate in a concrete carbonation test chamber at 20℃, 70% humidity, and 20% carbon dioxide concentration for 24 hours to remove the loose layer on the aggregate surface. Then, place the recycled aggregate in a vacuum drying oven and dry it at 80℃ and -0.08MPa vacuum for 2.5 hours to remove surface moisture. Subsequently, place it in a plasma treatment instrument, using argon as the gas source at 175W for 10 minutes to complete the pretreatment, improve the surface roughness and activity of the aggregate, and lay the foundation for subsequent spraying and bonding with auxiliary materials. S2. Prepare a nano-silica dispersion and spray it onto the surface of the pretreated recycled aggregate to form a nano-silica film. Let it air dry naturally for 30-60 minutes, and then spray the pre-ultrasonic dispersed nano-hydroxy magnesium silicate dispersion evenly to further fill the micropores on the surface of the aggregate, complete the modification and enhancement treatment of the recycled aggregate, and achieve a dual modification effect. S3. Add nano-hydroxy magnesium silicate to deionized water, then add 0.15% dispersant (compatible with water-reducing agent), and sonicate at 325W for 25 minutes. Then add 0.65% silane coupling agent KH-550 and stir at 60℃ for 1 hour to complete the surface activation of the modifier. Add the modified chitosan microspheres to a small amount of water, stir evenly and set aside to avoid nanoparticle aggregation and improve compatibility with the original raw materials. S4. Weigh 470 parts of geopolymer cementitious material, 1110 parts of modified and reinforced recycled aggregate, 685 parts of manufactured sand, 150 parts of water, 7.5 parts of water-reducing agent, and 3.2% of the mass of the geopolymer cementitious material pretreated with nano-sized hydroxyl magnesium silicate and 1.5% of the mass of the geopolymer cementitious material pretreated with modified chitosan microspheres; add the geopolymer cementitious material, manufactured sand and 75 parts of water to a mixer and mix to obtain a uniform mortar mixture. S5. Add the modified and reinforced recycled aggregate to the mortar mixture and stir at 350 rpm for 17 minutes to ensure that the aggregate and mortar are fully combined. Increase the speed to 550 rpm and slowly add the pretreated nano-hydroxy magnesium silicate and stir for 35 minutes. Then raise the temperature to 90°C, reduce the speed to 250 rpm, add the modified chitosan microspheres, 75 parts water and 7.5 parts water-reducing agent, and continue to stir evenly to obtain a stable concrete mixture. S6. Pour the concrete mixture into a mold and cure it for 10 days at 20℃ and ≥90% humidity. After curing, place the concrete product in a constant temperature curing chamber and cure it at 70℃ for 5 hours. Then, let it cool naturally to room temperature and irradiate it with ultraviolet light at a wavelength of 254nm and an irradiation intensity of 12mW / cm² for 12 minutes to further improve the stability, chloride ion penetration resistance and durability of the concrete, making it suitable for the high-salt and high-humidity coastal environment. This yields high-durability recycled polymer concrete for coastal engineering.

[0021] Example 2 In Example 2, the geopolymer cementitious material is 400 parts, the recycled aggregate is 1140 parts, the manufactured sand is 670 parts, the water is 160 parts, the water-reducing agent is 6.0 parts, the modifier is 2.5% of the mass of the geopolymer cementitious material, and the synergistic agent is 2.0% of the mass of the geopolymer cementitious material.

[0022] The only difference between Example 2 and Example 1 is the proportion of each component of the raw materials used, but both are within the protection scope of this invention.

[0023] Example 3 In Example 3, the geopolymer cementitious material is 550 parts, the recycled aggregate is 1090 parts, the manufactured sand is 700 parts, the water is 140 parts, the water-reducing agent is 8.3 parts, the modifier accounts for 4.0% of the mass of the geopolymer cementitious material, and the synergistic agent accounts for 1.0% of the mass of the geopolymer cementitious material.

[0024] The only difference between Example 3 and Example 1 is the proportion of each component of the raw materials used, but both are within the protection scope of this invention.

[0025] This invention modifies recycled aggregates by performing plasma pretreatment and supplementary spraying with nano-hydroxy magnesium silicate, forming a composite modification process of "carbonization-vacuum drying-plasma activation-dual spraying," which differs from existing conventional aggregate modification methods and enhances the bonding force between aggregates and cementitious materials. The "step-by-step compounding + variable temperature and speed stirring" process ensures uniform dispersion of all components (especially nano-auxiliaries), avoids agglomeration problems, and fully leverages the synergistic effect of auxiliary materials and original raw materials, overcoming the limitations of existing conventional stirring processes. The subsequent curing steps form a composite curing system of "conventional curing-low temperature curing-ultraviolet activation," specifically improving the durability and stability of concrete, making it suitable for harsh coastal environments.

[0026] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A high-durability recycled polymer concrete for coastal engineering, characterized in that: It is composed of geopolymer cementitious materials, recycled aggregates, manufactured sand, water, water-reducing agent, and auxiliary materials, wherein the auxiliary materials are modifiers and synergists; The geopolymer cementitious material is composed of industrial solid waste steel slag, gypsum, mineral powder, metal tailings and solid alkali activator; The recycled aggregate is produced from construction solid waste through crushing, washing, and sorting. The modifier is nano-sized magnesium hydroxysilicate; The synergistic agent is modified chitosan microspheres.

2. The high-durability recycled polymer concrete for coastal engineering according to claim 1, characterized in that: The composition of the geopolymer cementitious material is 400-550 parts, the composition of the recycled aggregate is 1090-1140 parts, the composition of the manufactured sand is 670-700 parts, the composition of the water is 140-160 parts, the composition of the water-reducing agent is 6.0-8.3 parts, the composition of the modifier is 2.5%-4.0% of the mass of the geopolymer cementitious material, and the composition of the synergistic agent is 1.0%-2.0% of the mass of the geopolymer cementitious material.

3. The high-durability recycled polymer concrete for coastal engineering according to claim 2, characterized in that: The modified chitosan microspheres were modified by γ-ray irradiation with a dose of 5-8 kGy.

4. A method for preparing high-durability recycled polymer concrete for coastal engineering, comprising using the high-durability recycled polymer concrete for coastal engineering as described in any one of claims 1-3, characterized in that: Includes the following steps, S1. Place the recycled aggregate in a concrete carbonation test chamber for 24 hours of carbonation treatment; then place the recycled aggregate in a vacuum drying oven for 2-3 hours to remove surface moisture. It is then placed in a plasma processor and treated for 8-12 minutes using argon as the gas source, thus completing the pretreatment. S2. Prepare a nano-silica dispersion and spray it onto the surface of the pretreated recycled aggregate to form a nano-silica film. Let it dry for 30-60 minutes, then spray a nano-hydroxy magnesium silicate dispersion to fill the micropores on the aggregate surface and complete the modification and reinforcement treatment of the recycled aggregate. S3. Add nano-hydroxy magnesium silicate to deionized water, then add dispersant and ultrasonically disperse. Subsequently, add silane coupling agent KH-550 and stir at 57-65℃ for 1-1.5h to complete the surface activation of the modifier. Add modified chitosan microspheres to water and stir evenly. S4. Weigh out the geopolymer cementitious material, recycled aggregate, manufactured sand, water, water-reducing agent and pretreated auxiliary materials according to the proportions. Add the geopolymer cementitious material, manufactured sand and 50% water to the mixer and mix to obtain a uniform mortar mixture. S5. Add the modified and reinforced recycled aggregate to the mortar mixture and stir at 300-400 rpm for 15-20 minutes. Then increase the speed to 500-600 rpm and add nano-hydroxy magnesium silicate and stir for 30-40 minutes. Then raise the temperature to 85-95℃, reduce the stirring speed to 200-300 rpm, add modified chitosan microspheres, water-reducing agent, and the remaining 50% of water and continue stirring to obtain the concrete mixture. S6. Pour the concrete mixture into a mold for curing at 18-22℃ and ≥90% humidity for 7-14 days. After curing, transfer it to a constant temperature curing chamber and cure at 68-75℃ for 4-6 hours. Then, allow it to cool naturally to room temperature for 12-15 hours. Finally, treat it with ultraviolet light to obtain high-durability recycled polymer concrete.

5. The method for preparing high-durability geopolymer recycled concrete for coastal engineering according to claim 4, characterized in that: In step S1, the temperature of the carbonization test chamber is 20℃, the humidity is 70%, and the carbon dioxide concentration is 20%; the temperature of the vacuum drying oven is 75-85℃, the vacuum degree is -0.08~-0.07MPa, and the drying time is 2-3 hours; the power of argon gas treatment is 150-200W.

6. The method for preparing high-durability geopolymer recycled concrete for coastal engineering according to claim 5, characterized in that: In step S2, after spraying the nano-silica dispersion, air dry for 30-60 minutes; in step S3, during ultrasonic dispersion, the power is 300-350W and the time is 20-30 minutes; the dispersant accounts for 0.1%-0.2% of the deionized water, and the silane coupling agent KH-550 accounts for 0.5%-0.8% of the deionized water.

7. The method for preparing high-durability geopolymer recycled concrete for coastal engineering according to claim 6, characterized in that: In step S6, the ultraviolet light irradiation treatment is carried out at a wavelength of 254nm, an irradiation intensity of 10-15mW / cm², and an irradiation time of 10-15min.

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